This invention relates generally to an implantable pacing lead for use with a cardiac pacemaker, and more specifically, to a pacing lead having a multilumen tubing for the lead body and at least one ring electrode or electrical contact located between the distal and proximal ends of the pacing lead.
Medical science has advanced the state-of-the-art of pacemakers and cardiac pacing, and the associated pacing leads, to the point where pacing leads requiring three or more electrical conductors are now in common use. In some instances, the electrical conductors are attached to ring electrodes spaced anywhere from a few millimeters to several centimeters behind the distal end of the pacing lead, and to electrical contacts at the proximal end of the lead. The electrodes may be used, for example, as the cathode or anode in a bipolar pacing configuration, or alternatively, as sensory electrodes to sense parameters, such as atrial electrical activity; ventricular electrical activity; and impedance changes to determine such parameters as cardiac stroke volume, respiration rate, or minute volume.
Various configurations have been proposed for assembling in-line or ring electrodes and electrical contacts, and for interconnecting them to conductors extending between the proximal and distal ends of the pacing lead. It has been known, for example, to use a multilumen silicone tube which is generally an elongated length of silicone tubing having multiple axially aligned channels or lumens extending therethrough. When the multilumen tubing is assembled with other components of the system, the individual conductors are inserted into the lumens of the multilumen tubing, and advanced to their point of interconnection to their respective electrodes/terminals.
At the point of interconnection of the multilumen tubing and a ring electrode or connector, it is necessary to provide a secure electrical connection between the conductor and the ring electrode, as well as to provide an assembly which will prevent invasion of body fluids into the lumens. Invasion and retention of body fluids within the lumens of the lead body threatens the viability and integrity of the pacing lead. This can be manifest, as in one example, by body fluid electrolytes entering the lead body and causing electrical shorting between conductors and/or electrodes.
Multilumen tubing has advantages with respect to its flexibility and biocompatibility which makes it particularly suitable for use in the construction of a pacing lead. Thus, a high integrity interconnection between the multilumen tubing and ring electrode is desirable.
The intended environment for the pacing lead, i.e. implanted within the body and inserted through a vein and on into the heart, subjects the pacing lead to repetitive flexure. This environment dictates that the interconnection of a ring electrode and the multilumen tubing of the lead body, as well as the electrical connection between the ring electrode and its respective conductor, will endure the repetitive flexure. Invasion of blood fluids about the edges of the ring electrode and into the lumens of the multilumen tubing must be prevented. In addition, electrical conductors which pass through the ring electrode must be electrically isolated from the ring electrode. Accordingly, the configuration of the interconnection point for a ring electrode and a multilumen tubing lead body is of critical importance.